The invention relates to methods of and to apparatus for ascertaining certain parameters of fibrous material, particularly tobacco, and for using the results to influence the quality of products which contain the fibrous material. More particularly, the invention relates to improvements in methods of and in apparatus for determining the hardness of finished and/or incipient cigarettes and like rod-shaped products of the tobacco processing industry for the purpose of influencing the quality of such products and of reducing the number of rejects. Still more particularly, the invention relates to improvements in methods of and in apparatus for measuring certain parameters (such as hardness) of cigarettes or like rod-shaped products of the tobacco processing industry while the products are in motion in a rod making or filter tipping machine.
Hardness is a very important parameter of each rod-shaped product of the tobacco processing industry (such products will be called cigarettes or filter cigarettes for short with the understanding, however, that the method and apparatus of the present invention can be used with equal or similar advantage in connection with the making and processing of plain or filter cigars, cigarillos, cheroots and other rod-shaped products of the tobacco processing industry). Hardness denotes the resistance which the fibrous material of the filler in a cigarette offers to elastic deformation, particularly to deformation by the fingers of the smoker. Hardness of a cigarette is strongly influenced by the filling power of fibrous material which forms the filler, i.e., the rod-shaped condensed stream of tobacco particles which is surrounded by a tubular wrapper of cigarette paper or other suitable wrapping material. The term filling power denotes the ability of a given quantity of fibrous material (normally tobacco) to create the impression that the wrapper is properly filled with such material. Thus, a person holding a cigarette and not knowing the exact quantity of tobacco particles which fill the wrapper will gain the impression that the cigarette is plump and well rounded if the filling power of tobacco forming the filler is satisfactory, i.e., even if the wrapper confines a relatively small quantity of tobacco. Consequently, if the filling power of tobacco is rather high, the hardness of such product is also satisfactory to the smoker because a large majority of smokers prefer cigarettes which offer a certain amount of resistance to deformation. The hardness of cigarettes is monitored and the results of such monitoring operation are utilized to ensure that the hardness is increased if the tested products are too soft.
In accordance with a known proposal, a cigarette rod making machine is equipped with means for ascertaining the hardness of a continuous cigarette rod before the rod is subdivided into plain cigarettes of unit length or multiple unit length. It is also known to ascertain the filling power of the stream of tobacco particles which advance toward the wrapping (rod forming) station where the stream is draped into a continuous web of cigarette paper or other wrapping material to form therewith a continuous cigarette rod. Such determination of the filling power of a stream of tobacco particles involves the application of pressure in order to ascertain the resistance of the stream to deformation, i.e., to indirectly determine the hardness of cigarettes by actually ascertaining the filling power of tobacco which forms the stream. Indirect determination of hardness necessitates a determination of the mass flow of tobacco particles.
It is further known to indirectly ascertain the filling power of tobacco particles by measuring the height of the freshly formed tobacco stream ahead of the surplus removing (trimming or equalizing) station where one or more rotary and/or otherwise movable trimming members remove the surplus, and by also measuring the height of the equalized stream ahead of the wrapping station where the equalized stream is converted into the filler of a continuous cigarette rod. Instead of or in addition to measuring the height of the untrimmed and trimmed stream, it is also known to ascertain the filling power by monitoring the mass flow of the stream and/or the resistance which the stream offers to penetration of air or another gaseous fluid. The directly or indirectly gained results of such measurements of the filling power of tobacco particles and/or of the hardness of cigarettes are compared with reference values denoting the desired filling power and/or hardness, and the rod making machine is adjusted when the results of measurements depart from the reference value. The adjustment is intended to ensure that the filling power of tobacco particles and/or the hardness of cigarettes will at least closely approximate an optimum value, i.e., that such parameters of the fibrous material and of the rod-shaped products will remain at least substantially constant.